Johne's disease (paratuberculosis) is a chronic, contagious infection with the acid-fast-staining bacillus Mycobacterium avium subsp paratuberculosis (M. ptb). The disease affects ruminants and is characterized by emaciation and intermittent diarrhoea or softening of faeces. Johne's disease is a major disease of cattle, sheep, goats, deer, and camels (Beeman et al, The Compendium 11, 1415 (1989)).
The currently favoured treatment is with a living vaccine (Neoparasec, Merial). This vaccine contains live organisms of the Weybridge strain, an attenuated strain of M. ptb. Killed vaccines are also known.
The existing vaccines have two disadvantages. Carcasses of animals treated with the vaccines contain whole organisms which are not readily distinguishable from tuberculosis organisms. In addition both types of vaccines leave injection site lesions which can be easily confused with tuberculosis lesions.
An object of the present invention is to prepare a vaccine against Johne's disease in which the above disadvantages are either not present or are reduced.